Understanding the total health burden of vaccine-preventable diseases (VPD), and the impact of vaccine policies on health care provision is critical to developing vaccine strategies. Our Rochester New Vaccine Surveillance Network (NVSN) site (a founding NVSN member), has demonstrated a large inpatient burden of VPD using population-based studies with molecular viral diagnosis. We propose to enhance our NSVN by measuring and comparing the total burden of VPDs in hospital, Emergency Department (ED), & outpatient care settings, and by studying the healthcare impact of current & new vaccine policies. Seven projects in 4 major areas are proposed, to determine the: A.) population-based burden in children ages 0<5y of acute respiratory infection from influenza (A,B), RSV (A,B), parainfluenza viruses (1,2,3), & human metapneumo- virus in the area's only 2 pediatric hospitals (300 samples/y), corresponding 2 EDs (300 sampies/y), & 6 outpatient sites (400samples/y); B.) changes in healthcare from the introduction of new vaccines/policies on both vaccine practices/vaccine coverage for influenza & pneumococcal (PCV7) vaccines and on community disease burden (e.g. otitis media after PCV7) (by performing 4000 chart reviews in 60 practices [>85% of the population of 2-5y-olds], and by analyzing a local insurance dataset [n=140,000, >70% of population] and national datasets); C.) influenza vaccine effectiveness in preventing hospital, ED, & outpatient visits (case- cohort studies-cases from all 3 healthcare settings, controls from community, and strata of all children ages 6-23m & high risk children ages 2-5y); D.) potential burden of rotavirus disease to prepare for population- based laboratory surveillance for soon anticipated new vaccines (dataset analyses and chart reviews). Our 5y-old NVSN has experienced personnel, accurate laboratory and surveillance techniques, and the ability to respond quickly to new needs. This proposal will provide information integral to developing sound polices consistent with national goals to preventing VPD in children.